The present invention disclosed herein relates to a gastric cancer cell line derived from a mouse deficient in E-cadherin and p53, and a use thereof, and more specifically, to a murine gastric cancer cell line NCC-S3/NCC-S3M, which shows a phenotype very similar to that of human gastric cancer due to the deficiency in E-cadherin and p53, which are the genes where mutations are most frequently observed in human diffuse-type gastric cancer, an immunotherapy using the gastric cancer cell line, and a method of evaluating the efficacies of therapeutic agents for treating gastric cancer and/or evaluating toxicities of the same.